Audio Power Amplifier Design Handbook This Page is Intentionally Left Blank Audio Power Amplifier Design Handbook Fourth edition Douglas Self MA, MSc AMSTERDAM•BOSTON•HEIDELBERG•LONDON•NEWYORK•OXFORD PARIS•SANDIEGO•SANFRANCISCO•SINGAPORE•SYDNEY•TOKYO NewnesisanimprintofElsevier NewnesisanimprintofElsevier LinacreHouse,JordanHill,OxfordOX28DP 30CorporateDrive,Burlington,MA01803 Firstpublished2006 Copyright©2006,DouglasSelf.Allrightsreserved TherightofDouglasSelftobeidentifiedastheauthorofthisworkhasbeen assertedinaccordancewiththeCopyright,DesignsandPatentsAct1988 Nopartofthispublicationmaybereproducedinanymaterialform(including photocopyingorstoringinanymediumbyelectronicmeansandwhetherornot transientlyorincidentallytosomeotheruseofthispublication)withoutthewritten permissionofthecopyrightholderexceptinaccordancewiththeprovisionsofthe Copyright,DesignsandPatentsAct1988orunderthetermsofalicenceissued bytheCopyrightLicensingAgencyLtd,90TottenhamCourtRoad,London, EnglandW1T4LP.Applicationsforthecopyrightholder’swrittenpermissionto reproduceanypartofthispublicationshouldbeaddressedtothepublisher PermissionsmaybesoughtdirectlyfromElsevier’sScienceandTechnologyRights DepartmentinOxford,UK:phone:(+44)(0)1865843830;fax:(+44)(0)1865 853333;e-mail:[email protected] on-lineviatheElsevierhomepage(http://www.elsevier.com),byselecting ‘CustomerSupport’andthen‘ObtainingPermissions’ BritishLibraryCataloguinginPublicationData Self,Douglas Audiopoweramplifierdesignhandbook.—4thed. 1. Audioamplifiers—Design 2. Poweramplifiers—Design I. Title 621.3′81535 LibraryofCongressControlNumber: 2006927666 ISBN-13:978-0-7506-8072-1 ISBN-10:0-7506-8072-5 ForinformationonallNewnespublications visitourwebsiteatwww.newnespress.com PrintedandboundinGreatBritain 06 07 08 09 10 10 9 8 7 6 5 4 3 2 1 Working together to grow libraries in developing countries www.elsevier.com | www.bookaid.org | www.sabre.org Contents Synopsis vii PrefacetoFourthEdition xvii Preface xviii 1. Introductionandgeneralsurvey 1 2. History,architectureandnegativefeedback 31 3. Thegeneralprinciplesofpoweramplifiers 62 4. Thesmallsignalstages 75 5. TheoutputstageI 109 6. TheoutputstageII 166 7. Compensation,slew-rate,andstability 186 8. PowersuppliesandPSRR 239 9. Class-Apoweramplifiers 259 10. Class-Gpoweramplifiers 294 11. Class-Damplifiers 319 12. FEToutputstages 328 13. Thermalcompensationandthermaldynamics 339 14. ThedesignofDCservos 385 15. Amplifierandloudspeakerprotection 397 16. Groundingandpracticalmatters 432 17. Testingandsafety 454 Index 464 v This Page is Intentionally Left Blank Synopsis Chapter 1 Introduction and general survey Theeconomicimportanceofpoweramplifiers Assumptions Originsandaims Thestudyofamplifierdesign Misinformationinaudio Scienceandsubjectivism TheSubjectivistposition Ashorthistoryofsubjectivism Thelimitsofhearing Articlesoffaith:thetenetsofsubjectivism Thelengthoftheaudiochain Theimplications Thereasonswhy Theoutlook Technicalerrors Theperformancerequirementsforamplifiers Safety Reliability Poweroutput Frequencyresponse Noise Distortion Dampingfactor Absolutephase Acronyms Chapter 2 History, architecture and negative feedback Abriefhistoryofamplifiers Amplifierarchitectures vii Synopsis Thethree-stagearchitecture Thetwo-stageamplifierarchitecture Poweramplifierclasses Class-A Class-AB Class-B Class-C Class-D Class-E Class-F Class-G Class-H Class-S VariationsonClass-B Error-correctingamplifiers Non-switchingamplifiers Current-driveamplifiers TheBlomleyprinciple GeometricmeanClass-AB Nesteddifferentiatingfeedbackloops AC-andDC-coupledamplifiers TheadvantagesofAC-coupling TheadvantagesofDC-coupling Negativefeedbackinpoweramplifiers Somecommonmisconceptionsaboutnegativefeedback AmplifierstabilityandNFB MaximisingtheNFB Maximisinglinearitybeforefeedback Chapter 3 The general principles of power amplifiers Howagenericamplifierworks Theadvantagesofconvention Theeightdistortions Distortionone:inputstagedistortion Distortiontwo:VASdistortion Distortionthree:outputstagedistortion Distortionfour:VASloadingdistortion Distortionfive:raildecouplingdistortion Distortionsix:inductiondistortion Distortionseven:NFBtakeoffdistortion Distortioneight:capacitordistortion Non-existentdistortions Theperformanceofastandardamplifier Open-looplinearityandhowtodetermineit viii Synopsis Directopen-loopgainmeasurement Usingmodelamplifiers Theconceptoftheblamelessamplifier Chapter 4 The small signal stages Theroleoftheinputstage Distortionfromtheinputstage BJTsvsFETsfortheinputstage AdvantagesoftheFETinputstage DisadvantagesofFETinputstage Singletoninputstageversusdifferentialpair Theinputstagedistortioninisolation Inputstagebalance Thejoyofcurrent-mirrors Improvinginput-stagelinearity Radicalmethodsofimprovinginputlinearity Inputstagecascodeconfigurations Inputnoiseandhowtoreduceit Offsetandmatch:theDCprecisionissue Theinputstageandtheslew-rate Thevoltage-amplifierstage MeasuringVASdistortioninisolation VASoperation VASdistortion LinearisingtheVAS:activeloadtechniques VASenhancements Theimportanceofvoltagedrive ThebalancedVAS TheVASandmanipulatingopen-loopbandwidth Manipulatingopen-loopbandwidth Conclusions Chapter 5 The output stage I Classesanddevices Thedistortionsoftheoutput Harmonicgenerationbycrossoverdistortion Comparingoutputstages Theemitter-followeroutput TheCFPoutput Quasi-complementaryoutputs Triple-basedoutputconfigurations TripleEFoutputstages Distortionanditsmechanisms ix